Regioisomers Salviprolin A and B, Unprecedented Rosmarinic Acid Conjugated Dinorditerpenoids from Salvia przewalskii Maxim

Salvia przewalskii Maxim is a perennial plant from the genus Salvia (family Lamiaceae). The roots of S. przewalskii were long used as a traditional herb to treat blood circulation related illnesses in China. As part of our continuing interest in polycyclic natural products from medicinal plants, two unprecedented adducts comprised of a dinor-diterpenoid and a 9′-nor-rosmarinic acid derivative, linked by a 1,4-benzodioxane motif (1 and 2), were isolated from the roots of S. przewalskii. Their structures were established by extensive spectroscopic approaches including 1D, 2D NMR, and HRFABMS. Their cytotoxic activities against five human tumor cell lines were evaluated.

Studies of Glyoxalase 1-Linked Multidrug Resistance Reveal Glycolysis-Derived Reactive Metabolite, Methylglyoxal, Is a Common Contributor in Cancer Chemotherapy Targeting the Spliceosome

BackgroundTumor glycolysis is a target for cancer chemotherapy. Methylglyoxal (MG) is a reactive metabolite formed mainly as a by-product in anaerobic glycolysis, metabolized by glyoxalase 1 (Glo1) of the glyoxalase system. We investigated the role of MG and Glo1 in cancer chemotherapy related in multidrug resistance (MDR).MethodsHuman Glo1 was overexpressed in HEK293 cells and the effect on anticancer drug potency, drug-induced increase in MG and mechanism of cytotoxicity characterized. Drug-induced increased MG and the mechanisms driving it were investigated and the proteomic response to MG-induced cytotoxicity explored by high mass resolution proteomics of cytoplasmic and other subcellular protein extracts. Glo1 expression data of 1,040 human tumor cell lines and 7,489 tumors were examined for functional correlates and impact of cancer patient survival.ResultsOverexpression of Glo1 decreased cytotoxicity of antitumor drugs, impairing antiproliferative activity of alkylating agents, topoisomerase inhibitors, antitubulins, and antimetabolites. Antitumor drugs increased MG to cytotoxic levels which contributed to the cytotoxic, antiproliferative mechanism of action, consistent with Glo1-mediated MDR. This was linked to off-target effects of drugs on glycolysis and was potentiated in hypoxia. MG activated the intrinsic pathway of apoptosis, with decrease of mitochondrial and spliceosomal proteins. Spliceosomal proteins were targets of MG modification. Spliceosomal gene expression correlated positively with Glo1 in human tumor cell lines and tumors. In clinical chemotherapy of breast cancer, increased expression of Glo1 was associated with decreased patient survival, with hazard ratio (HR) = 1.82 (logrank p < 0.001, n = 683) where upper quartile survival of patients was decreased by 64% with high Glo1 expression.ConclusionsWe conclude that MG-mediated cytotoxicity contributes to the cancer chemotherapeutic response and targets the spliceosome. High expression of Glo1 contributes to multidrug resistance by shielding the spliceosome from MG modification and decreasing survival in the chemotherapy of breast cancer. Adjunct chemotherapy with Glo1 inhibitor may improve treatment outcomes.

Two New Cytotoxic Maytansinoids Targeting Tubulin from Trewia nudiflora

Two new maytansinoids, N-methyltreflorine (1) and methyltrewiasine (2), were isolated from the dried fruits of Trewia nudiflora, together with three known congeners (3 – 5). Their structures were elucidated by spectroscopic methods, and the absolute configuration of 1 and 2 was determined by X-ray crystallographic analysis. Compounds 1 – 5 exhibited strong cytotoxicity against human tumor cell lines, including HeLa, MV-4 – 11, and MCF-7, with IC50 values ranging from 0.12 to 11 nM. Compounds 1 and 4 also showed inhibitory activity against the MCF-7/ADR cell line with IC50 values of 13 and 28 nM, respectively. Compounds 1 and 2 significantly inhibited tubulin polymerization in vitro with IC50 values of 3.6 and 3.2 µM, respectively.

Gold Nanorods are Selective Cytotoxic Agents

Background: Gold nanorods (GNRs) are very promising agents that have multiple applications in medicine and biology. However, the cytotoxic effects of GNRs have not been fully explored. Objective: Therefore, the main objective of this study was to determine the selective cytotoxic effect of GNRs towards several human tumor cell lines. Methods: To address this issue, three sizes of GNRs (10-nm, 25-nm, and 50-nm) were tested against two human tumor cell lines, namely, human hepatoma HepG2 and human prostate PC3 cancer cells. As GNRs are usually stored in soft tissues inside living bodies, we also tested the effect of GNRs on murine splenocyte viability. To determine if the GNRs displayed selectivity cytotoxicity towards cancer cells, active GNRs with the size showing the least cytotoxicity to splenocytes were then tested against a panel of 11 human tumor cell lines and two human non-tumor cell lines. Results: Our results showed that the most cytotoxic size of GNRs is 10-nm, followed by the 25-nm GNRs, while the 50-nm GNRs did not show a significant effect. In addition, the 25-nm GNRs were the least cytotoxic to splenocytes when tested for 24 and 48 h. These GNRs showed a selective cytotoxic effect to prostate cancer PC3 cells with median inhibitory concentration (IC50) = 8.3 + 0.37 µM, myeloblastic leukemia HL60 cells (IC50 = 19.7 + 0.89 µM), cervical cancer HeLa cells (IC50 = 24.6 + 0.37 µM), renal adenocarcinoma 786.0 cells (IC50 = 27.34 + 0.6 µM), and hepatoma HepG2 cells (IC50 = 27.79 + 0.03 µM) when compared to the effect on the non-tumor human cells; skin fibroblast BJ cell line (IC50 = 40.13 + 0.7 µM) or epithelial breast MCF10A cells (IC50 = 33.2 + 0.89 µM). A high selectivity indices (SI) were observed in GNRs-treated PC3 and HL60 cells with values ranging from 1.69 to 4.83, whereas moderate SIs were observed in GNRs-treated HeLa, 786.0, and HepG2 cells with values ranging from 1.19 to 1.63. Other cells did not show a similar selective effect, including human laryngeal HEp2 cells, colon HCT116, metastatic renal adenocarcinoma ACHN cells, and human breast cancer cells (MCF7, MDA-MB-231, and MDA-MB-468 cells). The effect of GNRs was confirmed using the colony formation assay and the effect was found to be cell cycle specific. Finally, it was shown that laser treatment can potentiate the cytotoxic effect of the 25-nm GNRs. Conclusion: GNRs are selective cytotoxic agents and they have the potential to act as candidate anticancer agents.

siRNAs Targeting Mouse-Specific lncRNA AA388235 Induce Human Tumor Cell Pyroptosis/Apoptosis

Species-specific lncRNAs significantly determine species-specific functions through various ways, such as epigenetic regulation. However, there has been no study focusing on the role of species-specific lncRNAs in other species yet. Here, we found that siRNAs targeting mouse-specific lncRNA AA388235 could significantly induce death of human tumor cells, although it has no effect on mouse tumor cells and normal human cells. The mechanism studies showed that these siRNAs could activate the response of human tumor cells to exogenous nucleic acids, induce pyroptosis and apoptosis in the presence of GSDME, but induce apoptosis in the absence of GSDME. They also significantly inhibited the growth of human tumor cells in vivo. 17 siRNAs were designed for seven more mouse-specific lncRNAs selected randomly, among which 12 siRNAs targeting five lncRNAs induced death in human tumor cell. Our study not only demonstrates that the siRNAs designed for knocking down mouse-specific lncRNA AA388235 can be potential tumor therapeutic drugs, but also suggests that non-human species-specific lncRNAs are a huge potential library that can be used to design siRNAs for tumor treatment. Large-scale screening based on this is promising.

Tetracyclic Thioxanthene Derivatives: Studies on Fluorescence and Antitumor Activity

Thioxanthones are bioisosteres of the naturally occurring xanthones. They have been described for multiple activities, including antitumor. As such, the synthesis of a library of thioxanthones was pursued, but unexpectedly, four tetracyclic thioxanthenes with a quinazoline–chromene scaffold were obtained. These compounds were studied for their human tumor cell growth inhibition activity, in the cell lines A375-C5, MCF-7 and NCI-H460. Photophysical studies were also performed. Two of the compounds displayed GI50 values below 10 µM for the three tested cell lines, and structure–activity relationship studies were established. Three compounds presented similar wavelengths of absorption and emission, characteristic of dyes with a push-pull character. The structures of two compounds were elucidated by X-ray crystallography. Two tetracyclic thioxanthenes emerged as hit compounds. One of the two compounds accumulated intracellularly as a bright fluorescent dye in the green channel, as analyzed by both fluorescence microscopy and flow cytometry, making it a promising theranostic cancer drug candidate.

Densazalin, a New Cytotoxic Diazatricyclic Alkaloid from the Marine Sponge Haliclona densaspicula

Densazalin, a polycyclic alkaloid, was isolated from the marine sponge Haliclona densaspicula collected in Korea. The complete structure of the compound was determined by spectroscopic methods, including 1D and 2D nuclear magnetic resonance techniques, high-resolution mass spectrometry, and comparison of the calculated and measured electronic circular dichroism spectra. Densazalin possesses a unique 5,11-diazatricyclo[7.3.1.02,7]tridecan-2,4,6-triene moiety, which is connected by two linear carbon chains. This compound was derived from the biogenetic precursor bis-1,3-dialkylpyridnium. Densazalin exhibited cytotoxic activity on two human tumor cell lines (AGS and HepG2) in the Cell Counting Kit-8 (CCK-8) bioassay, with IC50 values ranging from 15.5 to 18.4 μM.